Objectives: Tonic spinal cord stimulation (SCS) is currently used to treat neuropathic pain. With this type of stimulation, an implantable pulse generator generates electrical paresthesias in the affected area through 1 or more epidural leads. The goal of this study was to evaluate the impact of tonic SCS on the sensory perception of chronic pain patients using quantitative sensory testing (QST). Materials and Methods: Forty-eight patients (mean age: 57 y) with chronic leg pain due to failed back surgery syndrome or complex regional pain syndrome treated with SCS were recruited from 3 research centers. Test procedures included 2 sessions (stimulation On or Off), with measures of detection thresholds for heat, touch, vibration, and of pain thresholds for cold, heat, pressure, the assessment of dynamic mechanical allodynia, and temporal pain summation. Three different areas were examined: the most painful area of the most painful limb covered with SCS-induced paresthesias (target area), the contralateral limb, and the ipsilateral upper limb. Wilcoxon signed-rank tests were used to compare the mean difference between On and Off for each QST parameter at each area tested. P-values <0.05 were considered significant. Results: Regarding the mean difference between On and Off, patients felt less touch sensation at the ipsilateral area (−0.4±0.9 g, P=0.0125) and were less sensitive at the contralateral area for temporal pain summation (−4.9±18.1 on Visual Analog Scale 0 to 100, P=0.0056) with SCS. Discussion: It is not clear that the slight changes observed were clinically significant and induced any changes in patients’ daily life. Globally, our results suggest that SCS does not have a significant effect on sensory perception.

Standard treatment for cluster headache consists of abortive treatment with oxygen, triptans, ergot alkaloids and/or topical nasal local anesthetic during acute episodes and preventive treatment such as steroid injections, calcium channel blockers and lithium. Although the exact pathophysiology of cluster headache is not well understood, reduced serum levels of kynurenine metabolites with anti-NMDA (N-methyl-D-aspartate) properties have been demonstrated. Ketamine and magnesium, which both have potent anti-NMDA receptor activity, have been used in multiple refractory pain syndromes. We describe a case of cluster headache that was non-responsive to standard therapy and treated effectively with intravenous infusion of magnesium and ketamine.

INTRODUCTION:Despite numerous medical, pharmacological and surgical approaches for chronic low back pain (LBP), many patients continue to complain of severe disabling pain. Peripheral nerve field stimulation (PNfS), alone or combined with spinal cord stimulation, is a neuromodulation procedure that have been recently developed and implemented in our hospital. We conducted a Health Technology Assessment (HTA) to determine if PNfS may be considered as a standard of practice in the management of intractable LBP and failed back surgery syndrome (FBSS).METHODS:An interdisciplinary group of experts was involved in the project. A systematic review (SR) was performed in several databases and grey literature to identify clinical practice guidelines, SR and observational studies published through September 2016. A survey was conducted among other chronic pain centers in Canada to document PNfS use in LBP and FBSS treatment.RESULTS:Data on effectiveness and safety of PNfS in chronic LBP treatment were scarce. Short-term results (3-12 months) from small sample and low quality studies suggest that PNfS, alone or combined with spinal cord stimulation, is associated with pain intensity and opioid use reductions. Effects on functional status and quality of life remain undetermined. Most frequent adverse events reported with PNfS devices are lead migrations, discomfort or pain and surgical site infections. No other Canadian pain centers were found to use PNfS in chronic LBP or FBSS.CONCLUSIONS:PNfS is potentially a beneficial treatment option for patients with chronic low back pain or FBSS. However, the value of this innovative treatment remains unknown. Among factors to be clarified are target population (any chronic low back pain or FBSS), use of PNfS alone or combined with spinal cord stimulation, long-term effects, and comparison with conventional medical management. PNfS use in chronic LBP has to be assessed through a rigorous framework before its introduction as a standard medical practice.